Significance of AgNORs and Ki-67 Proliferative Markers in Differential Diagnosis of Thyroid Lesions

We aimed to assess the utility of quantitative analysis of AgNORs and Ki67 labeling index (LI) in the differential diagnosis of different thyroid lesions. This study included: 25 papillary carcinomas, 7 follicular carcinomas, 21 follicular adenomas and 27 nodular goiters. Using a semiautomatic image analysis system, Ag NORs parameters were measured and calculated including: total area of AgNORs, mean Ag NOR number in nuclei, nuclear area, mean area of AgNOR dots per each nucleus, number of central and marginal AgNOR dots, and the relative ratio of total area of AgNOR dots/total area of nucleus. Ki67 immunostaining was performed and the LI was determined. There was a significant difference between groups of thyroid lesions regarding total area of AgNORs, Ag NOR number and number of marginal Ag NOR dots. According to receiver operating characteristic curve, Ag NORs number =2.91 and marginal Ag NORs = 2.67 were useful cut off values above which follicular carcinoma can be diagnosed with 100 % sensitivity, 79 % specificity, 76 % PPV, 100 % NPV and 85 % diagnostic accuracy for both parameters. Mean Ki67 LI in our study was 14.12 +/- 2.29, 61.42 +/- 3.77, 34.90 +/- 3.49 and 18.60 +/- 1.96 for papillary carcinoma, follicular carcinoma, follicular adenoma and nodular goiter respectively. Ki67 LI showed statistically significant difference between follicular carcinoma and follicular adenoma (p = 0.026) and between papillary carcinoma and follicular adenoma (p = 0.007). Quantification of Ag NORs and Ki67 LI could be used as helpful ancillary methods in the differentiation between different thyroid lesions.